DIY Audio Projects Forum

Welcome to the DIY Audio Projects Message Forum. Use these forums to discuss Hi-Fi audio and to share your DIY Audio Projects. Registration is free and required to post messages and view the file attachments. Registration will only take a minute and registered users do not see any advertisements. After you have completed the online registration process, check your email (including spam/junk folder) for the verification email to activate your account. New members are under moderation - so your posts will not be visible until approved by a moderator. See the Read Me 1st, Forum RULES and Forum FAQ to get started on the forum.

Hi, Nice case. Makes my efforts with wood look like making orange crates. Anyhow, Some hiss is normal. I too have sensitive speakers (96dbw). A very slight amount of noise right at the speaker is common with tube amps. However, yours may be more than it ought to be. It may be from the driver tube. Not all are quiet and some actually quite noisy. There is another "trick" that may help. In some of my high gain phono preamp circuits I found the following can cut the noise by 2-3 db. It involves adding a capacitor from the heater circuit to signal ground. A 47uf seems to work best ...if it does anything. Sometimes nothing happens. Try both sides of the heater circuit one often is better than the other. This will only work if you are using DC heater power. I personally don't find it necessary as the slight noise is not audible at more than about 2cm from the tweeter. Let us know what you find.

Thanks for suggesting to add a 47uf capacitor from the driver tube's heater circuit to signal ground in order to try to remove the hiss.But to be sure, I have a question since the heater circuits are not grounded. Is this how it should be placed?

Thanks,

This post has a file attachment. Please login or register to access it. Only Registered Members may view attached files.

Hi Guys,Looking at the schematic shown above, there is a note that "the capacitor immediately after the LR8N should be the same size and type as the ones in the main amplifier". The schematic I have shows a 4.7uF on the output of the LR8, and a 1uF at the socket. Can somebody please advise which is correct? What type of capacitors should the 4.7 and 1 be? Also, the schematic I have shows a 1K from the 100uF capacitor feeding the 47uF filter capacitor. The diagram above shows a 33k. Which is correct?

Yes, the placement is right. Bruce mentioned that you should try both wires of heating power supply (you connect the capacitor to the "+" wire, you should try the "-" wire too and choose the connection with the best result).

Who is online

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot post attachments in this forum